Functional MRI

In the spring of 1991 the first of a group of new methods for mapping human brain function was successfully tested at the MRI Center of the Massachusetts General Hospital, in Boston. These methods use the supremely noninvasive technique of magnetic resonance imaging to create images of the brain that are sensitive to local changes in blood flow. In identification of cortical areas active for a particular brain task, they promise a spatial resolution of 2 mm, a temporal resolution of 1 s, and the opportunity to rescan a single subject as often as desired. As might have been expected, legions of brain researchers have since leapt upon magnetic resonance functional neuroimaging, or functional MRI (fMRI) as it is more frequently called, attempting to apply it to various studies in cognitive neuroscience. Whilst the underlying phenomenon is simple, in the sense that many MRI scanners were found to have the capability of performing fMRI studies once the technique had been discovered, quantification of the effect in relation to cortical electrical activity has been elusive, and for those unversed in MRI the origins of the functional signal require some explanation.